Limited supply of fossil energy resources and their associated global environmental damage have compelled market forces to diversify energy resources and related technologies. One such resource that has received significant attention is solar energy, which employs photovoltaic (PV) technology to convert light into electricity. Typically, PV production has been doubling every two years, increasing by an average of 48 percent each year since year 2002, making it the world's fastest-growing energy technology. By midyear 2008, estimates for cumulative global solar energy production capacity stands to at least 12,400 megawatts. Approximately 90% of such generating capacity consists of grid-tied electrical systems, wherein installations can be ground-mounted or built upon roofs or walls of a building, known as Building Integrated Photovoltaic (BIPV).
Moreover, significant technological progress has been achieved in design and production of solar panels, which are further accompanied by increased efficiency and reductions in manufacturing costs. In general, a major cost element involved in establishment of a wide-scale solar energy collection system is the cost of the support structure, which is employed to mount the solar panels of the array in proper position for receiving and converting solar energy. Other complexities in such arrangements involve efficient operations for the PV elements.
The PV elements for converting light to electric energy are often applied as solar cells to power supplies for small power in consumer-oriented products, such as desktop calculators, watches, and the like. Such systems are drawing attention as to their practicality for future alternate power of fossil fuels. In general, PV elements are elements that employ the photoelectromotive force (photovoltage) of the p-n junction, the Schottky junction, or semiconductors, in which the semiconductor of silicon, or the like, absorbs light to generate photocarriers such as electrons and holes, and the photocarriers drift outside due to an internal electric field of the p-n junction part.
One common PV element employs single-crystal silicon and semiconductor processes for production. For example, a crystal growth process prepares a single crystal of silicon valency-controlled in the p-type or in the n-type, wherein such single crystal is subsequently sliced into silicon wafers to achieve desired thicknesses. Furthermore, the p-n junction can be prepared by forming layers of different conduction types, such as diffusion of a valance controller to make the conduction type opposite to that of a wafer.
In addition to consumer-oriented products, solar energy collection systems are employed for a variety of purposes, for example, as utility interactive power systems, power supplies for remote or unmanned sites, and cellular phone switch-site power supplies, among others. An array of energy conversion modules, such as, PV modules, in a solar energy collection system can have a capacity from a few kilowatts to a hundred kilowatts or more, depending upon the number of PV modules, also known as solar panels, used to form the array. The solar panels can be installed wherever there is exposure to the sun for significant portions of the day.
Typically, a solar energy collection system includes an array of solar panels arranged in the form of rows and mounted on a support structure. Such solar panels can be oriented to optimize the solar panel energy output to suit the particular solar energy collection system design requirements. Solar panels can be mounted on a fixed structure, with a fixed orientation and fixed tilt, or can be mounted on a tracking structure that aims the solar panels toward the sun as the sun moves across the sky during the day and as the sun path moves in the sky during the year.
Nonetheless, controlling temperature of the photovoltaic cells remains critical for operation of such systems, and associated scalability remains a challenging task. Common approximations conclude that typically about 0.3% power is lost for every 1° C. rise in the PV cell.